Recently, construction machines have been commonly provided with a cab structure that is configured to protect an operator when the machines fall down. Accordingly, the roll over protective structure (ROPS) performance has been considered as an important factor. For example, a Japanese Patent Application Publication No. JP-A-2004-224083 discloses a cab structure of a construction machine, which is a frame structure formed by assembling a variety of pipe-shaped members in a basket shape. According to this type of structure, it is possible to remarkably enhance stiffness with respect to deformation that is caused when a construction machine falls down, compared to the cab structure made up only by the combination of sheet metal members.
On the other hand, construction machines, which are configured to be used in such a situation as the urban civil engineering, are often provided with a doorway through which an operator enters/exits and a sliding door for opening/closing the doorway. The sliding door is configured to be guided by a guide rail that is provided in the vicinity of the doorway so as to be disposed along the lateral surface of a cab, and is also configured to be allowed to move along the lateral side of the cab. Even when the construction machine is used in a narrow space where a road construction or the like is performed, the above described configuration makes it possible to prevent the opened door from protruding outside a swivel platform, and also makes it possible for an operator to easily get on and off the construction machine.